Current limiting circuit breaker mechanism



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CURRENT LIMITING CIRCUIT BREAKER MECHANISM 3 Sheets-Sheet 1 Filed Nov. 23, 1966 OFF- RESET EV.

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ELDO/V 5. HEFT A T' TO 'WE Y United States Patent M 3,384,346 CURRENT LIMITING CIRCUIT BREAKER MECHANISM Eldon B. Heft, West Hartford, Conn, assignor to General Electric Company, a corporation of New York Filed Nov. 23, 1966, Ser. No. 596,692 18 Claims. (Cl. 335-46) My invention relates to electric circuit breaker mechanisms, and more particularly to mechanisms for currentlimiting type circuit breakers.

Electric circuit breakers of conventional noneurrentlimiting type have historically included two types of means for causing opening of the circuit. The first of these means is a means which is under the control of an operator, and which ordinarily involves a handle which is manually thrown by the operator to move the contacts to open position, and is therefore referred to as manually operable means. (It will be appreciated, however, that the energy required to move the contacts to open circuit position may instead be supplied by some power means under the control of the operator, such as an eletcric motor.) The other means for causing opening of the contacts is means which operates automatically, that is, without waiting for a signal from a human agency, the signal being taken instead from the condition of the current which is pas-sing through the circuit breaker itself. Thus, the circuit breaker in effect monitors its own current and when the current exceeds a predetermined level for a predetermined time, the breaker automatically opens. This has ordinarily been accomplished by actuating the same mechanism which is involved in the manual opening operation. Thus the speed of opening of the contacts is about the same whether opening is initiated manually or automatically.

In current-limiting type circuit breakers, it is required that the contacts not only be openable at the will of an operator, and in response to abnormal magnitude current and current time conditions, but further, that the contacts should also be capable of opening, when a high short-circuit condition of predetermined abnormal magnitude occurs, at an ultra-high speed, which is much faster than would be permitted by the manual and conventional automatic operating mechanism. Such ultra-high speed opening of the contacts is therefore not possible by the use of the same mechanism which is required for automatic and manual operation.

Accordingly, in accordance with the prior art, mechanisms have been devised including (1) means providing for manual off-on operation of a movable contact, (2) means providing for automatic opening movement of the contact in response to medium and medium-high overload conditions with an inverse-time response characteristic, including magnetic operable means, and (3) means for causing high speed opening movement of the contacts despite the non-actuation of the aforesaid manual and automatic means, in response to the occurrence of shortcircuit conditions of predetermined exceptionally high magnitude. A mechanism of the type described is disclosed, for example, in co-pending application S.N. 491,- 840, filed Sept. 30, 1965, now Patent No. 3,315,189 and assigned to the same assignee as the present invention.

In accordance with the above-mentioned prior art current-limiting circuit breaker mechanisms, the movable contact member is connected to an actuating arm by means of a connecting link which can assume two rotational positions as determined thereby the condition of an overcenter spring which extends between the contact carrying member and the contact operating arm. Thus the contact carrying member is normally maintained in a first position with relation to the contact operating arm, but

3,384,846 Patented May 21, 1968 without movement of the contact operating arm, the contact carrying arm can be moved to a position in which the contact is retracted, by rotating the contact carrying link with respect to the contact carrying arm, moving the aforesaid spring overcenter in the process, the contact carrying link being thereafter maintained in this position by the overcenter action of the spring.

The aforesaid principle is subject to the disadvantage that if a contact retracting force, such as a contact blowout force or a contact-opening force generated by a special solenoid, etc., is of a predetermined intermediate magnitude, the movable contact member may be moved away from the stationary contact a small amount without moving the overcenter spring to its overcenter condition, and thereafter the movable contact member will return to its closed position. Such an occurrence can cause complete failure to interrupt a high short-circuit current, with consequent virtual destruction of the circuit breaker.

It is an object of the present invention to provide a current-limiting circuit breaker mechanism of the type which includes first means for moving the contact to open and closed circuit positions which first means includes means for manually as well as automatically operating the contacts in response to low and medium overload conditions and second means for moving the movable contact to open circuit position substantially independent of said first means, which will avoid the difficulty described above. that is, which will ensure that once the movable contact member begins to move in response to said second contact opening means it will continue its movement to open circuit position.

It is another object of the invention to provide mechanism of the type described which is simple, dependable in operation, and economical to manufacture.

It is a further object of the invention to provide a mechanism of the type described which will not vary in operation, that is, in which the amount of opening force required remains substantially constant regardless of wear of the contacts or wear of mechanism parts.

It is another object of the invention to provide a current-limiting circuit breaker of the type described which is capable of automatic opening by the aforesaid second means in response to high-short-circuit currents and also in response to lower magnitude short-circuit and overload currents in the range ordinarily detected by magnetic tripping means in a conventional or non-current-limiting circuit breaker, thereby making the inclusion of such magnetic tripping means unnecessary.

In accordance with the invention, an operating mechanism is provided of the general type described, in which the movable contact is operated by a contact operating arm through the agency of an intermediate or connecting link which has two possible positions with respect to the contact operating arm, which positions will be referred to as a latched position and 21 released position respectively. The connecting link is retained in the latched position by the action of a spring. Upon the occurrence of a predetermined high short-circuit current conditions, an opening force is exerted directly on the movable contact assembly. When this force reaches a predetermined level, it overcomes the latch retaining force of the aforesaid spring, whereupon the connccting link is moved out of latched relation which the contact operating arm and is thereafter acted on by the aforesaid spring, as well as by the aforesaid contact opening force, to move it to a retracted position with respect to the main contact operating arm. Thus the contact opening force is not reuired to move the movable contact to open position after the releasing of the latch has occurred. Moreover, no opening motion will occur under the force acting on the movable contact assembly is great enough to assure that release of the latch will occur, with consequent full opening action.

The invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.

In the drawings,

FIGURE 1 is a side elevation view of an electric circuit breaker incorporating the invention;

FIGURE 2 is a side elevation view on enlarged scale of the operating mechanism parts of the circuit breaker of FIGURE 1;

FIGURE 3 is a side elevation view of a portion of the mechanism of the circuit breaker of FIGURE 1, the parts being shown in the condition which they occupy in the closed or on condition of the contacts;

FIGURE 4 is a companion view of FIGURE 3, showing portions of the mechanism being broken away to reveal the location and construction of parts otherwise hidden in FIGURE 3;

FIGURE 5 is a side elevation view of a portion of the breaker mechanism, the parts being shown in the condition which they occupy when the contacts are in the open or off condition;

FIGURE 6 is a companion view to FIGURE 5 portions of the mechanism being broken away to reveal the location and construction of parts otherwise hidden in FIG- URE 5;

FIGURE 7 is a view similar to FIGURE 4 but omitting certain parts of the mechanism not involved in high-speed opening;

FIGURE 8 is a view similar to FIGURE 7 but showing the parts in the condition that they occupy in the high-speed automatically opened, or high-speed tripped condition;

FIGURE 9 is an end elevation view of the mechanism of the circuit breaker of FIGURE 1, partly in section, and

FIGURE 10 is a fragmentary, semi-diagrammatic illustration of the intermediate or connecting link, for explanatory purposes.

Referring to FIGURE 1, the invention is shown as incorporated in an electric circuit interrupter comprising an insulating casing having a base 10 and a cover, not shown. While the enclosure may take any of various forms, in FIGURE 1 the enclosure base 10 is shown as comprising a side wall 11 and having integral top and bottom walls 12 and 13, and also integral end walls 14 and 115. A line terminal 16 is positioned in a conforming recess in the base 10 and is connected by a terminal strap 17 to a first stationary contact 19 thereon. A second stationary contact 20 is supported on a similar confronting contact support and are runner 21 which in turn is connected by a conductor strap 22 which is mounted to the base 10 securely by suitable means such as by screws 23.

For the purpose of causing automatic operation of the mechanism, in a manner to be described, an elongated bimetallic strip 24 is provided which is fixedly mounted at one end to the conductor strap 22 by means of one of the screws 23, and has its other end free to move, and carrying an adjustable or calibrating screw 25. The bimetallic strip in turn is connected by means of a flexible braid 26 to an elongated conducting strap 27 to a first end 28 of a solenoid winding 29. The other end 30 of the winding 29 is in turn connected to the outgoing or load terminal 31.

The spaced stationary contacts 19 and 20 are interconnected, in the closed condition of the circuit breaker, by a pair of corresponding movable contacts 32, 33 carried by a generally wedge-shaped movable contact member 34.

The movable contact member 34 has an integral stem portion 35 extending in slidable relation within the end portion of a hollow contact operating rod 37. The pin 38 carried by the stem 35 has its opposite ends extending into a pair of slots 38 respectively in the rod 37 to limit the movement of the movable contact member 34. The contact stem 35 is biased outwardly of the rod 37 by a compression spring 46 positioned within the rod 37 and abutting against a stop pin 41 rigidly carried by the rod 37.

The contact operating rod 37 extends through the breaker mechanism and at its opposite end is connected to a solenoid plunger or armature 42 disposed to be attracted within the solenoid winding 29 upon sufiicient energization of the winding 29, for the purpose of providing high-speed opening of the contact in a manner to be more fully described.

In addition to the means for opening the contacts at high-speed comprising the solenoid 29, there is provided in accordance with the invention, means for manually operating the contacts between open and closed position and also for causing opening movement of the contacts upon the occurrence of small and medium overload conditions. For these purposes, mechanism is provided which will be referred to as manual and conventional-automatic opening mechanism. The manual and conventionalautomatic opening mechanism operates on the contact operating rod 37 as does the high-speed opening solenoid 29. Nevertheless, as noted previously, it is necessary that the high-speed opening solenoid be able to operate independently of the manual and conventional-automatic opening mechanism. In accordance with the invention, the manual and conventional-automatic opening automatic mechanism includes means providing for such in dependent action.

The manual and conventional-automatic opening mechanism will first be described, with reference particularly to FIGURES 1 and 2. A manually operable handle member 44 is provided, pivotally supported on a fixed pivot pin 45 which is carried by a generally U- shaped frame member 46 fixedly mounted in the casing 10. A manually engageable handle 47 is fixedly mounted on the member 44 and projects outwardly through an opening in the top wall 12 of the casing 10. The manually operable member 44 operates an upper pivot link 48 back and forth between off and on positions, to be described more fully, with an over-center action. For this purpose the operating member 44 is interconnected to the pivot link 48 by two pairs of tension springs 49, joined by means of triangular pieces 50, 51 to pins '52, 53 carried by the manually operable member 44 and by the link 48 respectively.

It should be understood that the operating mechanism is symmetrical, and includes two identical sets of parts, one disposed on each side of the contact operating rod 37. For convenience, the mechanism will be described with reference to FIGURE 2 and with reference to the parts on only one side of the operating rod 37.

The upper link 48 is pivotally supported on the normally fixed pivot 54 which is carried by a releasable member 55 which in turn is pivotally supported on a fixed pivot pin 56 fixedly supported by the side frames of the supporting frame 46.

As the manually operable member 44 and handle 47 are moved between on and off positions as indicated in FIGURE 1, therefore, the line of action of the tension springs 49 is moved from one side to the other of the pivot 54, thereby swinging the upper link 48 from one angular position to the other as shown, for example, in FIGURE 3 and FIGURE 5 respectively.

The upper link 48 does not directly engage the contact operating rod 37. Instead, the upper link 48 engages and actuates a lower link 58, which in turn is connected to the operating rod 37 in a manner to be described. The lower link 58 is pivotally supported on the fixed pivot 59 in the frame 46. The lower link carries an enlarged headed stud 60 which is slidably engaged by the upper link 48. Thus referring to FIGURES 3 and 5, the on and of conditions of these portions of the mechanism are illustrated.

Therefore, operation of the operating handle between on and off positions serves to swing the upper link 48 between on and off positions as shown in FIG- URES 3 and 5 particularly, which, in turn, moves the lower link 58 between corresponding on and off positions, the lower link 58 being connecting to the movable contact rod in a manner to be described, to operate the movable contact member 34 between open and closed circuit position.

CONVENTIONAL-AUTOMATIC OPENING As previously described, the releasable member 55 is pivotally supported on a fixed pivot pin 56 carried by the frame 46. It is maintained from rotation in clockwise direction about this pivot, however, by engagement of a latch end portion 55A with a latch member 62 which is pivotally supported on a fixed pivot 63 by the frame 46. The latch member 62 is biased in a clockwise direction by a compression spring 64, urging it against the calibrating screw 25 as a stop (see FIG. 1).

Upon the occurrence of sustained minor overload conditions, the bimetallic strip 24 becomes heated and warps so as to move the calibrating screw 25 to the left as viewed in FIGURE 1, rotating the latch member 62 counterclockwise against the bias of the spring 64, until the end portion 55A of the releasable member 55 is released. When this occurs, the upward bias of the tension springs 49, which is exerted on the link 48, and through the pivot 54 to the member 55, causes the member 55 to rotate in clockwise direction about its pivotal support 56. This action causes the pivot 54 to cross the line of action of the springs 49, thereby reversing the direction of the rotational bias of the springs 49 on the link 48, and rotating it clockwise about the pivot 54 to open circuit or conventionally-tripped position.

In order to reset the mechanism following conventional-tripping, the handle member 44 is moved counterclockwise slightly beyond the ofi position to reset position (see FIGURE 1). This causes the reset roller 44A to engage a edge portion 558 of the releasable member 55, rotating the member 55 in counterclockwise direc tion until the end 55A is once again in engagement with the latch 62.

It will be observed that tripping in the manner described under the action of the bimetallic strip 24 will take place whether or not the handle 47 is manually restrained in the on position. If desired, the action of the bimetallic strip 24 may be supplemented or entirely replaced by magnetic tripping means, not shown, similarly causing release of the latch 62 on the occurrence of minor overloads and minor short-circuits. It is a particular advantage of the present invention, however, that such supplementary magnetic tripping means need not be included in the conventional tripping mechanism, since, as will be described in greater detail, the latching arrangement of the high-speed or current-limiting tripping solenoid makes it possible to utilize this solenoid for both high short-circuits and for low short-circuits or high overload currents such as ordinarily detected by a conventional magnetic tripping means, i.e., one acting on the manual and conventional-automatic mechanism.

INDEPENDENT ACTIOIK OF HIGH-SPEED TRIP For the purpose of connecting the manual and conventional-automatic operating mechanism to the movable contacts in such a way as to permit independent opening movement of the movable contacts under the influence of the high-speed magnetic trip solenoid 29, a novel connection is employed in accordance with the invention between the lower toggle link 58 and the contact operating rod 37. This connection and its operation are specifically illustrated in FIGURES 7 and 8, and its coaction with the other parts illustrated in the other figures. The link 58 is connected to the operating rod 37 through the agency of an intermediate normally latched member 66. The member 66 has a slot 66A therein receiving one end of a fixed pin 67 carried by the rod 37.

The member 66 has a generally T-shaped configuration with a portion 663 extending at right angles to the remaining portion of the piece, which may be regarded as the stem of the T. The member 66 carries two spaced pins 69 and 70, the pin 70' being at the remote end of the portion 66B. The pins 69 and 70 ride in an elongated slot 71 in the link 58, and are biased by the tension spring 72 toward the left hand end of the slot 71 as viewed. Under normal operating conditions, the member 66 is retained in the position shown in FIGURES 2-7, in which the pin 70 is in a downwardly-directed portion 71A of the slot 71 (see FIG. 7). It will be observed that under these circumstances, the pull of the tension spring 72 on the pin 73 exerts a rotational 'bias on the piece 66, tending to rotate the member 66 about the pin 70 in clockwise direction. Such rotation is not permitted, however, by the engagement of the pin 69 with the upper surface of the slot 71. The part 66 therefore remains in the position shown.

From another point of view, it will be observed that since the pin 69 cannot move under these conditions, it may be regarded as fixed, and the bias of the spring 72 may be regarded as tending to rotate the member 66 clockwise about the pin 69, such rotation being prevented by the engagement of the pin 70 in the forward end 71A of the slot 71. It will moreover be observed that a pull exerted on the contact rod 37 to the left, exerts a force, through pin 67, tending to rotate the piece 66 counterclockwise about pin 69. If such force becomes great enough, it will be observed that this force will rotate the piece 66 counterclockwise about the pin 69 against the bias of the spring 72, thereby lifting the pin 70 out of the forward portion 71A of the slot 71.

During normal on-otf operation, however, as previously stated, the member 66 remains in its latched condition with the pin 70 in the forward part 71A of the slot '71, and the two parts 66 and 58 therefore operate as a single unit.

Upon the occurrence of extremely high short-circuit current conditions, however, the solenoid 29 greatly increases its pull and draws the solenoid armature or plunger 42 to the left as viewed in FIGURE 1. This draws the contact operating rod 37 to the left and causes the pin 67 to act on the member 66 to rotate the member 66 in counterclockwise direction about the pin 69 as previously described. This causes the forward pin 70 to move up out of the forward end 71A of the slot 71. When the pin 70 has moved upwardly sufliciently, it clears the shoulder of the slot 71, and the entire piece 66 is then free to move to the left as viewed, which it does, as indicated in FIG- URE 8. This movement moves the contact operating rod 37 and the movable contact assembly 32, 33, 34 to open circuit position. This construction in effect provides a force-defeatable or break-away connection between a movable contact member and a manually and automatically operable mechanism.

As shown in FIGURE 2, and previously described, the movable contact 34 is connected to the contact operating rod 37 by means of a lost-motion connection comprising pin 38 fixed to the contact stem 35 and having its end extending into the slots 38. The rod 37 normally acts to provide contact pressure through the agency of the compression spring 40 which is acted on by pin 41 carried by the rod 37. Initial opening movement of the rod 37 does not move the contact 34 until the lost motion provided in the slot 38' is taken up.

In accordance with the invention, the amount of lostmotion in the slot 38' is made such by comparison to the depth of the detent portion 71A of the slot 71, that the rod 37 must move far enough to move the pins 70 out of the detent portion 71A before the movable contact opens. Therefore, even if a short-circuit current force should prove to be just sufficient to separate the contacts, the detent will be disengaged, and the spring 72 will move the contacts to open condition. This assures that once the contacts separate due to a high-speed solenoid action, they will continue to move all the way open, and there will therefore be no opening and immediate reclosing. An important further advantage of this arrangement is that it makes it possible to use the same solenoid for relatively low short-circuit currents, thereby making it unnecessary to include magnetic tripping means in the conventional automatic opening mechanism. This is important since it is possible for the circuit interrupter to experience shortcircuit conditions which are marginal in the sense of cansin operation of the high-speed solenoid. In accordance with prior art structures, a high-speed actuation could permit partial separation of the contacts and followed by reclosing. This is extremely damaging to the contacts and to the entire circuit breaker.

In the present case, however, once the contact opening force is strong enough to cause opening movement of the contacts, the contacts are assured of moving the complete opened distance.

While the invention has been described in connection with only one specific embodiment, it will be readily apparent that many modifications thereof may readily be made. It is therefore intended by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A current-limiting circuit breaker comprising:

(a) a support;

(b) at least one pair of relatively movable contacts supported on said support;

(c) contact operating means supported on said support;

(d) connecting means connecting said contact operating means to said relatively movable contacts for operating said contacts between open and closed circuit positions;

(e) said connecting means comprising a driving member operably connected to said contact operating means and a driven member operably connected to said relatively movable contacts;

(f) means releasably interconnecting said driving and driven members comprising detent means carried by one of said driving and driven members and latching means connected to the other of said driving and driven members, said latching means having a portion engaging said detent means when said latching means is in a predetermined normal position, and

(g) means supporting said latching means for pivotal movement away from said normal position upon the exertion of predetermined force exerted on said driven member in contact-opening direction;

(h) current responsive means for exerting said predetermined force on said driven member in contact opening direction upon the occurrence of predetermined current conditions through said contacts, said latching means moving out of engagement with said detent means upon the occurrence of said predetermined forces and permitting movement of said driven member in contact opening direction substantially independently of said contact operating means.

2. A current-limiting circuit breaker as set forth in claim 1, said circuit breaker also comprising biasing means biasing said latch member for rotation about said pivotal supporting means toward said normal position at all times, said current responsive means acting on said latching means to move said latching means away from said normal position against the bias of said spring biasing means.

3. A current-limiting circuit breaker comprising:

(a) a support;

(b) at least one pair of relatively movable contacts supported on said support;

() contact operating means supported on said support;

(d) connecting means connecting said contact operating means to said relatively movable contacts for 8- operating said contacts between open and closed circuit positions;

(e) said connecting means comprising a driving member operably connected to said contact operating means and a driven member operably connected to said relatively movable contacts;

(f) means releasably interconnecting said driving and driven members comprising detent means carried by one of said driving and driven members and latching means connected to the other of said driving and driven members, said latching means having a portion engaging said detent means when said latching means is in a predetermined normal position, and

(g) means supporting said latching means for movement away from said normal position upon the exertion of predetermined force exerted on said driven member in contact-opening direction;

(h) spring biasing means biasing said latching means toward said normal position at all times, a current responsive means acting on said latching means to move said latching means away from said normal position, said spring biasing means acting on said driven member through the medium of said latching means following disengagement of said latching means from said detent means to assist movement of said driven member toward open circuit position.

4. A current-limiting electric circuit breaker as set forth in claim 3 wherein said latching means comprises a member pivotally and slidably connected to said driving member, said latching means moving pivotally with respect to said driving member prior to release of said latching means from said detent, said latching means moving slidably with respect to said driving member following release of said latching member from said detent.

5. A current-limiting circuit breaker as set forth in claim 3, said circuit breaker also comprising:

(a) means supporting said latching means on said driven member for pivotal movement prior to release of said latching means from said detent means;

(b) means supporting said latching means for sliding movement on said driving member following release of said latching means from said detent means;

(c) said latching member during said sliding movement moving said driven member in contact opening direction.

6. A current-limiting electric circuit breaker as set forth in claim 3, said circuit breaker also comprising:

(a) means pivotally supporting said latching means on said driving member prior to release of said latching means from said detent;

(b) means supporting said latching means on said driving member for slidable movement following disengagement of said latching means from said detent;

(c) spring biasing means biasing said latching member for pivotal movement in a direction to retain said latching means in engagement with said detent;

(d) means interconnecting said latching means and said driven member at all times;

(e) said spring means acting on said latch means following disengagement of said latch means from said detent means and biasing said latch means for movement in the direction of said slidable movement;

(f) said latch means acting on said driven member during said slidable movement to move said driven member in contact opening direction under the bias of said biasing spring.

7. A current-limiting electric circuit breaker as set forth in claim 3, wherein said circuit breaker also includes trip means for causing automatic contact opening operation of said contact operating means, and current responsive means for causing operation of said trip means.

8. A current-limiting electric circuit "breaker comprising:

(a) asupport;

(b) at least one stationary contact supported on said support;

(c) at least one movable contact supported on said support;

(d) contact operating means supported on said support;

(e) connecting means Connecting said contact operating means to said movable contact for operating said movable contact between open and closed circuit positions;

(f) said connecting means comprising a driving mem ber operably connected to said contact operating means and a driven member operably connected to said movable contact;

(g) means releasably interconnecting said driving and driven members comprising a latch member;

(h) means supporting said latch member on said driving member for slidable movement between 21 normal position and a released position;

(i) biasing means biasing said latch member for slidable movement from said normal position toward said released position;

(j) detent means normally restraining said latch member in said normal position;

(k) current-responsive means for exerting a predetermined force on said driven member in contact opening direction upon the occurrence of predetermined current conditions through said contacts;

(1) said latch member being releasable from said detent means upon the occurrence of predetermined force exerted thereon by said driven member.

9. A current-limiting electric circuit breaker as set forth in claim 8, in which said biasing means biases said latch member for rotation about said pivotal support onto engagement with said detent means while said latch member is in said normal position and biases said latch member for sliding movement away from said normal position following release of said latch member from said detent means.

10. A current-limiting electric circuit breaker as set forth in claim 8, in which said current responsive means acting on said driven member comprises an electric solenoid including a winding connected electrically in series with said movable contacts.

11. A current-limiting electric circuit breaker as set forth in claim 8, wherein said circuit breaker also includes second current responsive means for causing automatic contact opening operation .of said contact operating means.

12. A current-limiting electric circuit breaker comprising:

(a) asupport;

(b) at least one pair of relatively movable contacts supported on said support;

(c) first contact operating means supported on said support;

(d) said first contact operating means including manually operable means for moving said movable contacts between said closed and open circuit positions, and automatically operable means for moving said contacts between said open and closed circuit positions irrespective of the maintenance of said manually operable means in said closed circuit position;

(e) means interconnecting said first contact operating means and said movable contacts comprising a contact actuating member and a releasable interconnecting link;

(f) said contact actuating member and said releasable interconnecting link having a pair of interengaging portions normally in engagement with eaoh other when said contact actuating member and said interconnecting link are in normal position with relation to each .other, whereby motion of said contact actuating member in contact closing direction is transmitted through said connecting link to said relatively movable contacts;

(g) resilient means normally restraining said interconnecting link in said normal position with said interengaging portions in engagement with each other, when said relatively movable contacts are in said closed circuit position;

(h) means pivotally supporting said interconnecting link for pivotal movement relative to said contact actuating member when said contact actuating member is in said closed circuit position, said interconnecting link being rotatable about said pivotal support against the bias of said resilient means to move said interengaging portions out of engagement with each other;

(i) means supporting said interconnecting link for sliding movement relative to said contact actuating member following a disengagement of said interengaging portions to move said relatively movable contacts from said closed to said open circuit position despite the retention of said contact actuating member in said closed circuit position;

(j) and means responsive to a second type of abnormal electrical conditions in said circuit breaker for causing pivotal movement of said connecting link about said pivotal support in said releasing direction.

13. A current-limiting electric circuit breaker as set forth in claim 12, wherein said pivotal support of said interconnecting link comprises an interengagement of a portion of said interconnecting link with a portion of said contact actuating member.

14. A current-limiting electric circuit breaker as set forth in claim 12, wherein said relatively movable contacts are supported for straight-line reciprocal movement relative to each other, said relatively movable contact means comprising a pair of spaced stationary contacts and a single movable contact member having a pair of contact faces thereon co-acting with said spaced stationary contacts respectively, said bridging contact member being movable in reciprocal manner along a straight-line path, and having relatively low mass.

15. A current-limiting electric circuit interrupter comprising:

(a) a support;

(b) at least one pair of relatively movable contacts supported on said support;

(c) first contact operating means supported on said support;

'(d) means connecting said first contact operating means to said relatively movable contacts;

(e) first automatically operable means for moving said relatively movable contacts between open and closed circuit positions upon the occurrence of a first type of abnormal electrical conditions in said circuit breaker;

(f) means interconnecting said first automatically operable means and said relatively movable contacts;

(g) at least one of said first contact operating means and said first automatic contact operating means including a contact operating member having a releasable interconnecting link thereon, said contact operating member and said releasable interconnecting link having a pair of interengaging portions in engagement with each other when said contact actuating member and said interconnecting link are in normal position relative to each other whereby motion of said contact actuating member in contact closing direction is transmitted to said relatively movable contacts through said interconnecting link;

(h) resilient means normally restraining said interconnecting link in said normal position with said interengaging portions in engagement with each other;

(i) means pivotally supporting said interconnecting link for pivotal movement relative to said contact actuating member against the bias of said resilient means to move said inter-engaging portions out of engagement with each other;

(i) means supporting said releasable interconnecting link for sliding movement relative to said contact actuating member following disengagement of said inter-engaging portions to move said relatively movable contacts from said closed to said open circuit position;

(k) said biasing means acting on said releasable link in a direction to cause said pivotal movement of said releasable link in releasing direction and also to cause opening movement of said relatively movable contacts, second current responsive means responsive to a second type of abnormal current conditions for acting on said releasable connecting link against the bias of said biasing means to pivot said releasable connecting link to released position.

16. A current-limiting electric circuit breaker as set forth in claim 15, wherein said second current-responsive means comprises an electric solenoid.

17. A current-limiting electric circuit breaker as set forth in claim 15, wherein said biasing means acting on said releasable connecting link to hold said connecting link normally in said engaging position also acts on said releasable connecting link when released from said interengaging portions to assist sliding movement of said releasable connecting link and movement of said relatively movable contacts, without a substantial change of the line of action of said biasing means.

18. A current-limiting electric circuit breaker as set forth in claim 15, wherein said first contact operating means includes means positively restraining said contact actuating member in said closed circuit position whereby contact opening force exerted upon said relatively movable contact member does not cause movement of said contact actuating member from said closed circuit toward said open circuit position.

References Cited UNITED STATES PATENTS 2,601,484 6/1952 Wood 335-16 3,012,118 12/1961 Edmunds 33516 3,315,189 4/1967 Heft et a1. 33516 BERNARD A. GILHEANY, Primary Examiner.

H. BROOME, Assistant Examiner. 

3. A CURRENT-LIMITING CIRCUIT BREAKER COMPRISING: (A) A SUPPORT: (B) AT LEAST ONE PAIR OF RELATIVELY MOVABLE CONTACTS SUPPORTED ON SAID SUPPORT; (C) CONTACT OPERATING MEANS SUPPORTED ON SAID SUPPORT; (D) CONNECTING MEANS CONNECTING SAID CONTACT OPERATING MEANS TO SAID RELATIVELY MOVABLE CONTACTS FOR OPERATING SAID CONTACTS BETWEEN OPEN AND CLOSED CIRCUIT POSITIONS; (E) SAID CONNECTING MEANS COMPRISING A DRIVING MEMBER OPERABLY CONNECTED TO SAID CONTACT OPERATING MEANS AND A DRIVEN MEMBER OPERABLY CONNECTED TO SAID RELATIVELY MOVABLE CONTACTS; (F) MEANS RELEASABLY INTERCONNECTING SAID DRIVING AND DRIVEN MEMBERS COMPRISING DETENDENT MEANS CARRIED BY ONE OF SAID DRIVING AND DRIVEN MEMBERS AND LATCHING MEANS CONNECTED TO THE OTHER OF SAID DRIVING AND DRIVEN MEMBERS, SAID LATCHING MEANS HAVING A PORTION ENGAGING SAID DETENT MEANS WHEN SAID LATCHING MEANS IS IN A PREDETERMINED NORMAL POSITION, AND (G) MEANS SUPPORTING SAID LATCHING MEANS FOR MOVEMENT AWAY FROM SAID NORMAL POSITION UPON THE EXERTION OF PREDETERMINED FORCE EXERTED ON SAID DRIVEN MEMBER IN CONTACT-OPENING DIRECTION; (H) SPRING BIASING MEANS BIASING SAID LATCHING MEANS TOWARD SAID NORMAL POSITION AT ALL TIMES, A CURRENT RESPONSIVE MEANS ACTING ON SAID LATCHING MEANS TO MOVE SAID LATCHING MEANS AWAY FROM SAID NORMAL POSITION, SAID SPRING BIASING MEANS ACTING ON SAID DRIVEN MEMBER THROUGH THE MEDIUM OF THE SAID LATCHING MEANS FOLLOWING DISENGAGEMENT OF SAID LATCHING MEANS FROM SAID DETENT MEANS TO ASSIST MOVEMENT OF SAID DRIVEN MEMBER TOWARD OPEN CIRCUIT POSITION. 